What does that mean? How do I let him know I’m mad at him?

I am talking to a guy everyday, he always texts me first and he acts like he is very interested. But sometimes his answers become dry and he replies with one message every five hours. I see he's online, but he doesn't text back. A few days later, he texts me first (a lot of messages) and says he missed me :) and acts like nothing happened :) . It happens pretty often. What does that mean? How do I let him know I’m mad at him? I tried to do the same thing (ignoring him after he ignores me). I thought he will stop doing it, but it doesn't help.
What does that mean? How do I let him know I’m mad at him?
Post Opinion